Exercise 1: Getting Started
a. Create a JUnit Test Case for the c2f method in the
SampleMethods class. That is,
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Select >
.
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Pick a sensible name for your test class, such as
C2FTest.
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Make sure that the class being tested is
taojava.labs.testing.SampleMethods.
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Click the Next > button.
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Tick the box next to
c2f.
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Click the Finish button.
b. Click the Run button and observe what
happens.
c. Replace the body of the testC2F (or just
test) method with assertEquals(0,0).
Then click the Run button and observe
what happens.
d. Create a second method that looks like the following:
public void test2() {
fail("Not yet implemented");
} // test2()
e. What do you expect to happen when you run your test?
f. Check your answer experimentally.
g. Insert the annotation @Test before the declaration
of test2. Then determine what happens
when you run your test code.
h. Change the body of test2 to the following. Then
observe what happens when you run your test code.
assertEquals("stupid test", 10, 3*5);
Yes, this test is supposed to fail. It's there
to demonstrate that (a) you can add a message
to assertEquals, (b) you can include
computations in the body of assertEquals, and
(c) assertEquals treats the first non-message
value as the expected value and the second value as the received value.
Exercise 2: Temperature Conversion
You've seen how Eclipse lets you create and run tests. Now it's
time to write a few of your own.
a. We know that 0 degrees Celsius is 32 degrees Fahrenheit. Write
a test that verifies that SampleMethods.c2f computes the
expected value.
b. We know that 100 degrees Celsius is 212 degrees Fahrenheit. Write
a test that verifies that SampleMethods.c2f computes the
expected value.
c. Run your tests.
d. If your tests reveal errors in c2f, correct the code.
Then run the tests again.
e. Write any other tests you think are relevant. If the tests
reveal errors, correct the code and then run the tests again.
Exercise 3: Testing Simple Sums
a. Read the documentation for sum
b. Create a new test class and write some simple tests for
sum. Note that you can create an
array of integers with the following instruction.
int[] values = { 1, 2, 3 };
c. Attempt to fix any errors that your tests revealed.
d. Write a few more tests. Fix any more errors that you notice.
e. Consider the following test. Does it meet the preconditions
of sum? Do you expect your code to pass
the test?
public static void testExtremes() {
int tmp = Integer.MAX_VALUE - 10;
int[] values = { tmp, tmp, -tmp, -tmp };
asssertEquals("extreme test", 0, sum(values));
} // testExtremes
f. If your code does not pass the test, you have multiple options.
One option is to fix your code to handle situations like this. Another
is to rewrite the preconditions (e.g., "For every subset of ints,
the sum of that subset is greater than Integer.MIN_VALUE
and less than Integer.MAX_VALUE). Another is to say that
the test is so stupid that it shouldn't matter. Which do you prefer?
Exercise 4: Writing Multiple Test Cases
Read the documentation for the expt method.
Rather than writing individual test cases for this function, we should
be able to write a loop that does multiple test cases. Something
like the following:
Let expected be 1
For power = 0 to K
Confirm that expected = expt(2,power)
expect = expected * 2
a. Create a new test class and then add a test that follows that
strategy.
b. Determine if expt works as advertised.
It probably won't. But debugging the code is a task for another day.
Instead, we're going to write more tests.
c. Right now, your test only uses a base of 2. Rewrite your test so that
it tries multiple bases, both positive and negative.
